package com.reign.ast.sdk.alipay;

/**
 * base64
 * @author zhouwenjia
 * 
 */
public final class Base64 {
	
	static private final int BASELENGTH = 128;  
    static private final int LOOKUPLENGTH = 64;  
    static private final int TWENTYFOURBITGROUP = 24;  
    static private final int EIGHTBIT = 8;  
    static private final int SIXTEENBIT = 16;  
    static private final int FOURBYTE = 4;  
    static private final int SIGN = -128;  
    static private final char PAD = '=';  
    static private final boolean fDebug = false;  
    static final private byte[] base64Alphabet = new byte[BASELENGTH];  
    static final private char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];  
    static{  
        for (int i = 0; i < BASELENGTH; ++i){  
            base64Alphabet[i] = -1;  
        }  
        for (int i = 'Z'; i >= 'A'; i--){  
            base64Alphabet[i] = (byte) (i - 'A');  
        }  
        for (int i = 'z'; i >= 'a'; i--){  
            base64Alphabet[i] = (byte) (i - 'a' + 26);  
        }  
        for (int i = '9'; i >= '0'; i--){  
            base64Alphabet[i] = (byte) (i - '0' + 52);  
        }  
        base64Alphabet['+'] = 62;  
        base64Alphabet['/'] = 63;  
        for (int i = 0; i <= 25; i++){  
            lookUpBase64Alphabet[i] = (char) ('A' + i);  
        }  
        for (int i = 26, j = 0; i <= 51; i++, j++){  
            lookUpBase64Alphabet[i] = (char) ('a' + j);  
        }  
        for (int i = 52, j = 0; i <= 61; i++, j++){  
            lookUpBase64Alphabet[i] = (char) ('0' + j);  
        }  
        lookUpBase64Alphabet[62] = (char) '+';  
        lookUpBase64Alphabet[63] = (char) '/';  
    }  
      
      
    private static boolean isWhiteSpace (char octect){  
        return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);  
    }  
      
      
    private static boolean isPad (char octect){  
        return (octect == PAD);  
    }  
      
      
    private static boolean isData (char octect){  
        return (octect < BASELENGTH && base64Alphabet[octect] != -1);  
    }  
    
    /**
     * 编码
     * @param binaryData
     * @return
     */
    public static String encode (byte[] binaryData){  
        if (binaryData == null){  
            return null;  
        }  
        int lengthDataBits = binaryData.length * EIGHTBIT;  
        if (lengthDataBits == 0){  
            return "";  
        }  
        int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;  
        int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;  
        int numberQuartet = fewerThan24bits != 0? numberTriplets + 1 : numberTriplets;  
        char encodedData[] = null;  
        encodedData = new char[numberQuartet * 4];  
        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;  
        int encodedIndex = 0;  
        int dataIndex = 0;  
        if (fDebug){  
            System.out.println ("number of triplets = " + numberTriplets);  
        }  
        for (int i = 0; i < numberTriplets; i++){  
            b1 = binaryData[dataIndex++];  
            b2 = binaryData[dataIndex++];  
            b3 = binaryData[dataIndex++];  
            if (fDebug){  
                System.out.println ("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);  
            }  
            l = (byte) (b2 & 0x0f);  
            k = (byte) (b1 & 0x03);  
            byte val1 = ((b1 & SIGN) == 0)? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);  
            byte val2 = ((b2 & SIGN) == 0)? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);  
            byte val3 = ((b3 & SIGN) == 0)? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);  
            if (fDebug){  
                System.out.println ("val2 = " + val2);  
                System.out.println ("k4   = " + (k << 4));  
                System.out.println ("vak  = " + (val2 | (k << 4)));  
            }  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];  
        }  
        // form integral number of 6-bit groups   
        if (fewerThan24bits == EIGHTBIT){  
            b1 = binaryData[dataIndex];  
            k = (byte) (b1 & 0x03);  
            if (fDebug){  
                System.out.println ("b1=" + b1);  
                System.out.println ("b1<<2 = " + (b1 >> 2));  
            }  
            byte val1 = ((b1 & SIGN) == 0)? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];  
            encodedData[encodedIndex++] = PAD;  
            encodedData[encodedIndex++] = PAD;  
        } else if (fewerThan24bits == SIXTEENBIT){  
            b1 = binaryData[dataIndex];  
            b2 = binaryData[dataIndex + 1];  
            l = (byte) (b2 & 0x0f);  
            k = (byte) (b1 & 0x03);  
            byte val1 = ((b1 & SIGN) == 0)? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);  
            byte val2 = ((b2 & SIGN) == 0)? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];  
            encodedData[encodedIndex++] = PAD;  
        }  
        return new String (encodedData);  
    }  
    
    /**
     * 解码
     * @param encoded
     * @return
     */
    public static byte[] decode (String encoded){  
        if (encoded == null) {  
            return null;  
        }  
        char[] base64Data = encoded.toCharArray ();  
        // remove white spaces   
        int len = removeWhiteSpace (base64Data);  
        if (len % FOURBYTE != 0) {  
        	// should be divisible by four   
            return null;
        }  
        int numberQuadruple = (len / FOURBYTE);  
        if (numberQuadruple == 0){  
            return new byte[0];  
        }  
        byte decodedData[] = null;  
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;  
        char d1 = 0, d2 = 0, d3 = 0, d4 = 0;  
        int i = 0;  
        int encodedIndex = 0;  
        int dataIndex = 0;  
        decodedData = new byte[(numberQuadruple) * 3];  
        for (; i < numberQuadruple - 1; i++){  
            if (!isData ((d1 = base64Data[dataIndex++])) || !isData ((d2 = base64Data[dataIndex++])) || !isData ((d3 = base64Data[dataIndex++])) || !isData ((d4 = base64Data[dataIndex++]))){  
            	// if found "no data" just return null   
            	return null;  
            }
            b1 = base64Alphabet[d1];  
            b2 = base64Alphabet[d2];  
            b3 = base64Alphabet[d3];  
            b4 = base64Alphabet[d4];  
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);  
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));  
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);  
        }  
        if (!isData ((d1 = base64Data[dataIndex++])) || !isData ((d2 = base64Data[dataIndex++]))){  
        	// if found "no data" just return null   
        	return null;
        }  
        b1 = base64Alphabet[d1];  
        b2 = base64Alphabet[d2];  
        d3 = base64Data[dataIndex++];  
        d4 = base64Data[dataIndex++];  
        if (!isData ((d3)) || !isData ((d4))){
        	// Check if they are PAD characters   
            if (isPad (d3) && isPad (d4)){  
                if ((b2 & 0xf) != 0) { 
                	// last 4 bits should be zero   
                    return null;  
                }  
                byte[] tmp = new byte[i * 3 + 1];  
                System.arraycopy (decodedData, 0, tmp, 0, i * 3);  
                tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);  
                return tmp;  
            } else if (!isPad (d3) && isPad (d4)){  
                b3 = base64Alphabet[d3];  
                if ((b3 & 0x3) != 0) {
                	// last 2 bits should be zero   
                    return null;  
                }  
                byte[] tmp = new byte[i * 3 + 2];  
                System.arraycopy (decodedData, 0, tmp, 0, i * 3);  
                tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);  
                tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));  
                return tmp;  
            } else{  
                return null;  
            }  
        } else { 
        	// No PAD e.g 3cQl   
            b3 = base64Alphabet[d3];  
            b4 = base64Alphabet[d4];  
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);  
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));  
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);  
        }  
        return decodedData;  
    }  
    
    /**
     * 移除空格
     * @param data
     * @return
     */
    private static int removeWhiteSpace (char[] data){  
        if (data == null){  
            return 0;  
        }  
        // count characters that's not whitespace   
        int newSize = 0;  
        int len = data.length;  
        for (int i = 0; i < len; i++){  
            if (!isWhiteSpace (data[i])){  
                data[newSize++] = data[i];  
            }  
        }  
        return newSize;  
    }  
}
